Tri-Rotor Aircraft Capable of Vertical Takeoff and Landing and Transitioning to Forward Flight

ABSTRACT

Systems, methods, and devices provide a vehicle, such as an aircraft, with rotors configured to function as a tri-copter for vertical takeoff and landing (“VTOL”) and a fixed-wing vehicle for forward flight. One rotor may be mounted at a front of the vehicle fuselage on a hinged structure controlled by an actuator to tilt from horizontal to vertical positions. Two additional rotors may be mounted on the horizontal surface of the vehicle tail structure with rotor axes oriented vertically to the fuselage. For forward flight of the vehicle, the front rotor may be rotated down such that the front rotor axis may be oriented horizontally along the fuselage and the front rotor may act as a propeller. For vertical flight, the front rotor may be rotated up such that the front rotor axis may be oriented vertically to the fuselage, while the tail rotors may be activated.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a continuation of, and claims the benefit ofpriority to, U.S. Non-Provisional patent application Ser. No. 15/080,167“Tri-Rotor Aircraft Capable of Vertical Take-Off and Landing andTransitioning to Forward Flight,” which is a continuation-in-part of,and claims the benefit of priority to, U.S. non-provisional patentapplication Ser. No. 14/121,001 entitled “Vertical Take-Off and LandingVehicle with Increased Cruise Efficiency” filed Aug. 13, 2014, issued onOct. 25, 2016, as U.S. Pat. No. 9,475,579, which claims the benefit ofand priority to U.S. provisional patent application No. 61/865,347entitled “Benefits of Hybrid-Electric Propulsion To Achieve 4× IncreaseIn Cruise Efficiency for a VTOL Aircraft” filed on Aug. 13, 2013, andwhich claims the benefit of priority to U.S. provisional patentapplication No. 62/137,634 entitled “Tri-Rotor Aircraft Capable ofVertical Takeoff and Landing and Transitioning to Forward Flight” filedMar. 24, 2015. The entire contents of all four applications are herebyincorporated by reference in their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention described herein was made in part by employees of theUnited States Government and may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefore.

BACKGROUND OF THE INVENTION

Vertical takeoff and landing (“VTOL”) and cruise efficiency arediametrically opposed requirements for aircraft. There are systemsolutions today that require ground infrastructure, namely catapults andarresting equipment, to launch and recover cruise efficient aircraft,thereby imparting these aircraft with VTOL like capabilities. Thesecurrent multi-part systems remove the need for the actual aircraft toperform VTOL, but the system as a whole (i.e., aircraft plus groundinfrastructure) becomes a VTOL system. With these current systems it isnot possible to meet both VTOL and cruise efficiency requirementswithout the use of ground infrastructure.

Fixed wing aircraft are faster and more fuel efficient than rotarywinged aircraft, while rotary winged aircraft can hover and do notrequire long runways for takeoff and landing. Many potential missionsmake aircraft combining these features desirable, but current aircraftconfigurations that are capable of vertical takeoff and transitioning tohorizontal flight, including tilt-rotors, tilt-wings, and tail-sittersusually result in significant compromises in the performance of theaircraft in both the VTOL and horizontal flight modes because of thecompeting requirements of VTOL and efficient forward flightcapabilities. For example, tail-sitters have relatively poor stabilityat landing because the center of gravity is relatively high, andtail-sitters are limited to small aircraft because the tail structuremust support the weight of the aircraft. Additionally, the fuselage oftail-sitters is vertical on the runway limiting the types of cargo thatmay be carried. Tilt-rotors and tilt-wings provide vertical takeoff andtransition, but are complex designs that present challenges withpackaging the mechanisms for tilting inside the aircraft wing.

BRIEF SUMMARY OF THE INVENTION

The systems, methods, and devices of the present invention combine anadvanced vehicle configuration, such as an advanced aircraftconfiguration, with the infusion of electric propulsion, therebyenabling a four times increase in range and endurance while maintaininga full vertical takeoff and landing (“VTOL”) and hover capability forthe vehicle. In this manner, various embodiments may provide vehicles,such as aircraft, with both VTOL and cruise efficient capabilities thatmay meet VTOL and cruise efficiency requirements without the use ofground infrastructure. The various embodiments may provide a VTOL andcruise efficient vehicle, such as an aircraft, comprising a wingconfigured to tilt through a range of motion, a first series of electricmotors coupled to the wing and each configured to drive an associatedwing propeller, a tail configured to tilt through the range of motion, asecond series of electric motors coupled to the tail and each configuredto drive an associated tail propeller, and an electric propulsion systemconnected to the first series of electric motors and the second seriesof electric motors. In a further embodiment, the electric propulsionsystem may be a battery augmented series hybrid electric propulsionsystem comprising one or more internal combustion engines, one or moregenerators coupled to the one or more internal combustion engines andconnected to the first series of electric motors and the second seriesof electric motors, and one or more batteries connected to the firstseries of electric motors and the second series of electric motors.

The systems, methods, and devices of the present invention provide avehicle, such as an aircraft, with rotors configured to function as atri-copter for VTOL and a fixed-wing vehicle for forward flight. In anembodiment, one rotor may be mounted at a front of the vehicle fuselageon a hinged structure controlled by an actuator to tilt from horizontalto vertical positions. In an additional embodiment, two additionalrotors may be mounted on the horizontal surface of the vehicle tailstructure with rotor axes oriented vertically (e.g., perpendicular) tothe fuselage. In an embodiment, for forward flight of the vehicle, thefront rotor may be rotated down such that the front rotor axis may beoriented horizontally (e.g., parallel) along the fuselage and the frontrotor may act as a propeller, while the tail rotors may be deactivated.In an embodiment, for vertical flight, the front rotor may be rotated upsuch that the front rotor axis may be oriented vertically (e.g.,perpendicular) to the fuselage, while the tail rotors may be activated.

These and other features, advantages, and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification, claims, andappended drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, illustrate exemplary embodiments of theinvention, and together with the general description given above and thedetailed description given below, serve to explain the features of theinvention.

FIG. 1 is a component block diagram illustrating a front/left upperperspective view of an embodiment VTOL and cruise efficient aircraft.

FIG. 2 is a component block diagram illustrating a front/right lowerperspective view of the embodiment VTOL and cruise efficient aircraft.

FIG. 3 is a top view of an embodiment of a pylon for the presentinvention.

FIG. 4 is a component block diagram illustrating a front view of theembodiment VTOL and cruise efficient aircraft.

FIG. 5 is a component block diagram illustrating a left side view of theembodiment VTOL and cruise efficient aircraft in a VTOL flight phase.

FIG. 6 is a component block diagram illustrating a left side view of theembodiment VTOL and cruise efficient aircraft transitioning between theVTOL flight phase and a wing born flight phase.

FIG. 7 is a component block diagram illustrating a left side view of theembodiment VTOL and cruise efficient aircraft in the wing born flightphase.

FIG. 8 is a component block diagram illustrating a top view of anembodiment tri-rotor vehicle.

FIG. 9A is a component block diagram illustrating a front/left upperperspective view of the embodiment tri-rotor vehicle.

FIG. 9B is a component block diagram illustrating a front/left upperperspective view of the embodiment tri-rotor vehicle in a VTOL flightphase.

FIG. 10 is a component block diagram illustrating a front view of theembodiment tri-rotor vehicle.

FIG. 11 is a component block diagram illustrating a rear/left upperperspective view of the embodiment tri-rotor vehicle.

FIG. 12 is a component block diagram illustrating a left side view ofthe embodiment tri-rotor vehicle in a VTOL flight phase.

FIG. 13 is a component block diagram illustrating a left side view ofthe embodiment tri-rotor vehicle transitioning between the VTOL flightphase and a wing born flight phase.

FIG. 14 is a component block diagram illustrating a left side view ofthe embodiment tri-rotor vehicle in the wing born flight phase.

FIG. 15 is a component block diagram illustrating a front/left upperperspective view of a second embodiment tri-rotor vehicle in a wing bornflight phase.

FIG. 16 is a component block diagram illustrating a front/left upperperspective view of the second embodiment tri-rotor vehicle in a VTOLflight phase.

FIG. 17 is a component block diagram illustrating a left side view ofthe second embodiment tri-rotor vehicle in a VTOL flight phase.

FIG. 18 is a component block diagram illustrating a front/left upperperspective view of a third embodiment tri-rotor vehicle in a VTOLflight phase.

FIG. 19 is a component block diagram illustrating a front/left upperperspective view of the third embodiment tri-rotor vehicle in a wingborn flight phase.

FIG. 20 is a component block diagram illustrating a top view of thethird embodiment tri-rotor vehicle in a wing born flight phase.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of description herein, it is to be understood that thespecific devices and processes illustrated in the attached drawings, anddescribed in the following specification, are simply exemplaryembodiments of the inventive concepts defined in the appended claims.Hence, specific dimensions and other physical characteristics relatingto the embodiments disclosed herein are not to be considered aslimiting, unless the claims expressly state otherwise.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any implementation described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other implementations.

The various embodiments will be described in detail with reference tothe accompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.References made to particular examples and implementations are forillustrative purposes, and are not intended to limit the scope of theinvention or the claims.

Electric propulsion may enable radical new vehicle concepts andconfigurations, particularly for vertical takeoff and landing (“VTOL”)aircraft because electric propulsion may address the significantmismatch between takeoff and cruise power conditions experienced by VTOLaircraft. The ability to distribute the thrust across the airframe,without mechanical complexity and with a scale free propulsion system,may provide a new degree of freedom for aircraft designers.

The various embodiment vehicle configurations may combine an advancedvehicle configuration, such as an advanced aircraft configuration, withthe infusion of electric propulsion, thereby enabling a four timesincrease in range and endurance while maintaining a full VTOL and hovercapability (similar to the VTOL and hover capabilities of a helicopter)for the vehicle. In this manner, various embodiments may providevehicles, such as aircraft, with both VTOL and cruise efficientcapabilities that may meet VTOL and cruise efficiency requirementswithout the use of ground infrastructure. Cruise efficient vehicles,such as cruise efficient aircraft, may provide various efficienciesbased on the vehicle mission, such as reduced energy consumption duringflight, long range, and/or long endurance. The various embodiments mayalso provide the ability to achieve low disc-loading for low groundimpingement velocities, low noise, and/or hover powerreduction/minimization which may reduce energy consumption in a VTOLphase of flight.

The systems, methods, and devices of the various embodiments may providea VTOL and cruise efficient vehicle, such as an aircraft, comprising awing configured to tilt through a range of motion, a first series ofelectric motors coupled to the wing and each configured to drive anassociated wing propeller, a tail configured to tilt through the rangeof motion, a second series of electric motors coupled to the tail andeach configured to drive an associated tail propeller, and an electricpropulsion system connected to the first series of electric motors andthe second series of electric motors. In a further embodiment, theelectric propulsion system may be a battery augmented series hybridelectric propulsion system comprising one or more internal combustionengines, one or more generators coupled to the one or more internalcombustion engines and connected to the first series of electric motorsand the second series of electric motors, and one or more batteriesconnected to the first series of electric motors and the second seriesof electric motors.

Electric propulsion may be scale-free in terms of being able to achievehighly similar levels of motor power to weight and efficiency across adramatic scaling range. Using distributed electric propulsion may enablethe various embodiment advanced aircraft configurations to achieveimprovements in aerodynamic efficiency that may be approximately fourtimes that of conventional helicopter configurations. Helicopterstypically achieve a Lift to Drag ratio (L/D) of between 4 and 5, whilethe various embodiment VTOL aircraft may achieve an L/D of 15 to 20,such as 15, approximately 15, 15-17, 17-20, approximately 15 toapproximately 20, approximately 20, etc. The various embodiments providethe ability to eliminate the problem of advancing and retreating rotorblades by converting into wing born flight without the mechanicalcomplexity of previous VTOL aircraft.

The various embodiments may utilize hybrid electric propulsion tonormalize the power across the mission phases and to enable thecombustion engine to be sized for wing born flight and batteries may beused to supplement the power required in hover. This may yield anoverall lighter propulsion system, which may make for a smalleraircraft, which may lead to lower cost.

In an embodiment, an aircraft may have one or more propellers, such asone, two, three, four, five, six, seven, eight, nine, ten, or morepropellers, and one or more electric motors may distribute thrust acrossthe propellers. For example, the electric motors may distribute thrustacross ten propellers. In an embodiment, propellers may be mounted tothe leading edge of the wing of the aircraft and mounted to the leadingedge of the tail of the aircraft. The number of propellers mounted tothe leading edge of the wing of the aircraft and the leading edge of thetail of the aircraft may vary. For example, in an embodiment in whichthe aircraft may have ten propellers, eight propellers may be mounted tothe leading edge of the wing and two propellers may be mounted to theleading edge of the tail of the aircraft. In an embodiment, at least aportion of the wing of the aircraft and at least a portion of the tailof the aircraft may both tilt to transition the aircraft betweenhovering flight and wing born flight. In an embodiment, the wing of theaircraft and the tail of the aircraft may both rotate around the lateralaxis of the wing and tail, respectively, to tilt the wing and tailthrough a range of motion, thereby pitching the wing and tail up and/ordown relative to the longitudinal axis of the aircraft to transition theaircraft between hovering flight (i.e., the VTOL phase) and wing bornflight (i.e., the wing born flight phase). The range of motion may beany range of motion, such as less than 90 degrees, 90 degrees,approximately 90 degrees, greater than 90 degrees, etc. The tiltingportions of the wing of the aircraft and the tail of the aircraft maytilt together or independently and may tilt to the same or differentorientations in their respective ranges of motion.

In an embodiment, an aircraft may include a semi-tandem wingconfiguration. The semi-tandem wing configuration may provide acompromise between a tandem wing configuration, which carries half thelift on the tail, and a conventional wing configuration, which carriesno lift on the tail. The center of gravity of the embodiment aircraftwith the semi-tandem wing configuration may be located aft of the wing.The embodiment semi-tandem wing configuration may cause some lift to becarried on the tail of the aircraft, which may allow the propellers onthe tail to carry some the aircraft's weight during a hover in the VTOLflight phase. For example, the tail may carry less than fifty percent ofthe lift. However, the wing may carry most of the lift of aircraft. Theembodiment semi-tandem wing configuration may enable the wing to beproportionally larger than the tail and achieve a greater span in orderto reduce induced drag. In an embodiment, the aircraft may be designedsuch that the center of gravity location is selected to have thepropellers on the wing carry a higher percent of the aircraft's weightthan the propellers on the tail. In this manner, the propellers on thetail may provide greater pitch control authority and reduce induced dragof the tail by reducing the amount of lift that may be required to becarried on the tail. The embodiment semi-tandem wing configuration witha lifting tail may be statically stable in the wing born flight phase(i.e., forward flight). In an embodiment, the aircraft may be designedsuch that the lift coefficient, tail loading, and lift curve slope ofthe tail may be less than the lift coefficient, wing loading, and liftcurve slope of the wing. In an embodiment, the aircraft may include aswept wing to shift the aerodynamic center of the wing aft in forwardflight and still keep the center of thrust forward in hovering flightwhen the wing is rotate up 90 degrees. In an embodiment, the sweep ofthe wing may enable a reduction in the induced drag of the aircraft.During a hover, propeller thrust needs to be distributed about thecenter of gravity of the aircraft. Without a swept wing, in forwardflight the wing stays in front of the center of gravity resulting inonly about eighty percent of the lift on the wing and twenty percent onthe tail. However, in an embodiment with a swept wing, in a hover, thepropellers are forward of the wing, but in forward flight the wingcenter is farther aft enabling ninety two percent of the lift to be onthe wing and eight percent to be on the tail. Since the swept wing hashigher span (i.e., lower span loading), it is more efficient to carrylift on the wing.

In an embodiment, forward flight propellers may be located at the wingtips of the aircraft. The wing tip forward flight propellers may providea destructive interference between the propeller swirl and the wing tipvortex. The resulting interference may be viewed as an induced dragreduction or a propulsive efficiency increase. In an embodiment, theforward flight propellers may run for the entire mission (i.e., bothduring the VTOL flight phase and the wing born flight phase). In anembodiment, the forward flight propellers may run only during the wingborn flight phase. In an embodiment, the forward flight propellers maybe variable speed (e.g., variable revolutions per minute (“RPM”)) and/orvariable pitch propellers. The use of variable speed and/or pitchpropellers may maximize propulsive efficiency.

In an embodiment, vertical flight propellers may fold down during thewing born flight phase. In an embodiment, the vertical flight propellersmay fold into conformal recesses of the motor pylons. The folding of thevertical flight propellers, especially into conformal recesses, mayreduce drag in the wing born flight phase when compared to leaving thevertical flight propellers deployed. In an embodiment, the verticalflight props may extend aft of the leading edge of the wing and/or tailwhen folded. In an embodiment, to prevent the vertical flight propellersfrom contacting the leading edge of the wing as the vertical flightpropellers are started, the vertical flight propeller blades may ridealong a sinusoidal cam to push the blades forward enough to avoidcontact with the leading edge of the wing and/or tail.

In an embodiment, the propellers may be synchronized electronically tohold a specific phase angle to provide destructive interference of eachpropeller's noise. This may result in a quieter aircraft as a wholerelative to the sound generated by each propeller in isolation. In anembodiment, each successive propeller may rotate in an alternatedirection to prevent the wake of one propeller blade impacting the wakeof the adjoining propeller blade. In this manner, the wakes of thepropellers may pass in the same direction as opposed to colliding headon.

In an embodiment, the aircraft may include reflexed flaperons. The useof reflexed flaperons may delay the onset of stall on the wing duringtransition between the VTOL flight phase and the wing born flight phase.As discussed herein, “flaperons” refers to any control surface used asboth ailerons and flaps. By having reflexed (i.e., trailing edge up)flap deflections, the reflexed flaperons reduce the circulation aroundthe airfoil allowing the airfoil to go to a higher angle of attackbefore airflow separates.

In an embodiment, when the tail is tilted vertically in the VTOL flightphase, the vertical tail may serve a second role as a rear landing skid.In an embodiment, the wing tip motor pylons may serve as outboardlanding skids, thereby giving the aircraft a wide stance on the groundto reduce tip over risk at landing.

In an embodiment, a dihedral may be configured in the outboard portionof the horizontal tail to provide directional stability during the slowspeed portion of the transition corridor between the VTOL flight phaseand the wing born flight phase.

In an embodiment, an aircraft may utilize a battery augmented serieshybrid electric propulsion system. This use of a battery augmentedseries hybrid electric propulsion system may reduce propulsion systemweight and enable unconventional configurations. In an embodiment, allpropellers may be turned by electric motors. In an embodiment,electrical power to operate each motor may be provided from one or bothof two sources. A first source may be a primary electrical sourcecomprised of generators driven by internal combustion engines. A secondelectrical source may be battery packs. In an embodiment, the internalcombustion engines may be sized to meet the power requirements duringthe wing born flight phase, but the power required in the VTOL flightphase and during transition may be greater than the power required inthe wing born flight phase. The battery packs may be sized to make upfor the difference between the power required in the VTOL flight phaseand during transition and the power the internal combustion engines mayprovided by turning the alternators. This embodiment configuration maysupport the minimum propulsion system weight (as opposed to sizing theinternal combustion engines for power required for VTOL flight) formissions where the time spent in hover may be a small percent of thetime spent in wing born flight. The embodiment series hybrid propulsionsystem may effectively act as an “electric driveshaft” and an “electricgearbox” eliminating the driveshafts and gear boxes necessary todistribute power to each propeller in previous aircraft by filling thesame function. In an embodiment, in hovering flight the internalcombustion engines may turn generators, and the electrical power fromthe generators may be fed to a controller that outputs uniform directcurrent (“DC”) power. The DC power may be distributed via wiresthroughout the aircraft. The DC power may be provided to a motorcontroller associated with each motor which may convert the DC power toalternating current (“AC”) power to drive the AC motors turning thepropellers. The advantage of converting the AC output of the generatorsto DC power and the converting the DC power to AC power at each motormay be that the motor controller for each motor may independently driveits associated motor allowing the RPM to be varied on a per motor basis.The use of two controllers may result in some power loss due to theinefficiency of the controllers. In an embodiment, in wing born flightthe internal combustion engines may turn the generators and the AC poweroutput by the generators may be provided via wires directly to themotors without using intermediate controllers, thereby operating thegenerators and motors in a synchronous mode. This may avoid controllerloss. The RPM of the generator may need to be equal to the RPM of themotor being driven or if the pole count of the generator is differentthan the pole count of the motor, the ration of the motor to generatorRPM may be the ratio of the motor to the generator pole count.

In an embodiment, the use of electric motors to drive the propellers mayprovide an aircraft with a propulsion system that has no single point offailure. The use of multiple electric motors may enable the failure ofone motor to occur and the aircraft to still fly. Because electricmotors may put out more power by turning at a higher RPM, in the eventof a motor failure, other propellers, as required, may be turned at ahigher RPM by their respective motors ensuring the aircraft may still beflyable. The increase of RPM may put out more thrust per remainingpropeller (meaning also more noise), but the aircraft may remainflyable.

In an embodiment, the propellers of the aircraft may turn at a low tipspeed, enabling the aircraft to achieve a very low noise profile.

The various embodiments may provide a vehicle, such as an aircraft, withrotors configured to function as a tri-copter for VTOL and a fixed-wingvehicle for forward flight. In an embodiment, one rotor may be mountedat a front of the vehicle fuselage on a hinged structure controlled byan actuator to tilt from horizontal to vertical positions. In anadditional embodiment, two additional rotors may be mounted on thehorizontal surface of the vehicle tail structure with rotor axesoriented vertically (e.g., perpendicular) to the fuselage.

In an embodiment, for forward flight of the vehicle, the front rotor maybe rotated down such that the front rotor axis may be orientedhorizontally (e.g., parallel) along the fuselage and the front rotor mayact as a propeller, while the tail rotors may be deactivated. Forexample, when the tail rotors are deactivated the tail rotors may bestowed in pods, allowed to weathervane, oriented such that the long axisis aligned with the air flow (e.g., via the use of the motor magnets,external magnets, or other fixtures), or otherwise operate in anunpowered mode. During forward flight control surfaces, such asailerons, rudders, elevators, etc., may control the vehicle movementand/or orientation.

In an embodiment, for vertical flight, the front rotor may be rotated upsuch that the front rotor axis may be oriented vertically (e.g.,perpendicular) to the fuselage, while the tail rotors may be activated.The elevators on the tail may be rotated down, such as close tovertical, to reduce or prevent obstruction of the air flow from the tailrotors. The elevators on the tail may be independently deflectingelevators. Differential thrust may be produced by varying the speed orblade pitch (e.g., collectively and/or independently) of the threerotors (i.e., the front rotor and two tail rotors), and the thrustproduced by the three rotors may enable vertical motion of the vehicle,as well as pitch, roll, and/or horizontal motion. Yaw may be controlledby differentially actuating the left and right elevators to move themtoward or away from the vertical position, by actively tilting the tailrotors side to side, and/or actively tilting the tail rotors forward andaft to provide yaw torque. Yaw torque may also be achieved by mountingthe tail rotors with an outward cant angle.

In an embodiment, during transition from vertical flight to forwardflight, the front rotor angle may be changed as the front rotor isrotated from a position the where the front rotor axis may be orientedvertically (e.g., perpendicular) to the fuselage down to a positionwhere the front rotor axis may be oriented horizontally (e.g., parallel)along the fuselage, and the front rotor speed, tail rotor speeds, and/orelevator collective angles may be adjusted to maintain altitude andpitch stability while the vehicle accelerates forward.

The various embodiment tri-rotor design vehicles may enable a largerfront rotor than may be used on conventional fixed front propelleraircraft because the front rotor may rotate parallel to the groundduring take-off and landing. In this manner, the larger diameter rotormay provide an advantage of noise reduction for the various embodimenttri-rotor design vehicles compared to conventional fixed front propelleraircraft.

Cyclic pitch control may not be required on any of the rotors, but maybe added to/used with any of the rotors to provide control torques. Thevarious embodiment tri-rotor design vehicles may provide simplerhovering and transitioning vehicle designs by providing only a singlemechanism for tilting a propeller, requiring fewer mechanisms thantilt-rotor or tilt-wing designs. Additionally, cyclic pitch control maynot be required. The various embodiment tri-rotor design vehicles maykeep the vehicle fuselage horizontal during forward flight and verticalflight, thereby allowing an unobstructed field of view for cameras andother sensors, as well as a constant orientation for a communicationsantenna. As compared to a tail-sitter design, the various embodimenttri-rotor design vehicles with horizontal fuselage during VTOL mode mayenable better vehicle stability at landing due to the lower center ofgravity, vertical g-load on the payload at all time which may beadvantageous for human pilots and passengers, closer payload position tothe ground after landing, and/or better scalability resulting from lowertail structural loads. Additionally, the VTOL configuration may reduceground support requirements, for example, by eliminating the need forcatapult launchers, reducing runway length, and/or eliminating the needfor a landing recovery system.

The various embodiment tri-rotor design vehicles may be suitable for usein missions requiring hover capabilities, such as photography of aremote site, which may also benefit from added range, as well asmissions involving taking off without an airport or runway, includingprivate or roadable aircraft application, bush aircraft, etc.Additionally, the various embodiment tri-rotor design vehicles may besuitable for autonomous (unmanned) missions to place payloads at extremedistances from a launch and recover site.

Unique wind tunnel testing that combines a nested face-centered designof experiments (“DOE”) with optimal design points to achieve testingefficiency and statistically sound mathematical models was developed.This methodology required new tools and specialized tunnel software toexecute the experiment, such as allowing randomized set points, as wellas substantial automation of both the wind tunnel model and testfacility. The new methodology reduced testing time by over sixty years.

The applications for the various embodiment aircraft that may take offand land vertically and yet fly for a long duration and range arenumerous. Applications may range from military reconnaissance missions,to police and fire department surveillance roles, to civilian automateddoor to door package delivery (e.g., mail, prescription drugs, food,etc.), to air taxi services.

FIGS. 1-7 illustrate various views of an embodiment VTOL and cruiseefficient vehicle, such as aircraft 100. FIG. 1 is a component blockdiagram illustrating the front/left upper perspective view of theembodiment aircraft 100 with the wing (comprised of wing sections 101 aand 101 b) and horizontal tail sections 102 a and 102 b (comprising thetilting portions of the overall tail comprised of tiltable horizontaltail sections 102 a and 102 b and vertical tail section 102 c whichremains fixed) in the wing born flight phase configuration (i.e., tilteddown parallel to the longitudinal axis of the fuselage 160). In anembodiment, the aircraft 100 may include four engine nacelles on eachwing section 102 a and 102 b and one engine nacelle on each tailhorizontal tail section 102 a and 102 b. The engine nacelles may becomprised of pairings of pylons 103, 104, 105, 106, 107, 108, 109, 124,132, and 133 and respective fairings 111, 114, 113, 112, 115, 110, 117,116, 130, and 131. In an embodiment, each of the pylons 103, 104, 105,106, 107, 108, 109, 124, 132, and 133 may have the same outside moldline (“OML”) while each of the fairings 110, 111, 112, 113, 114, 115,116, 117, 130, and 131 may have its own OML. Electric motors may becoupled to each pylon 103, 104, 105, 106, 107, 108, 109, 124, 132, and133 to drive a propeller associated with each nacelle. Pylons 108, 106,104, 124, 132, 103, 105, 107, 109, and 133 are illustrated with theirrespective electric motors 138, 140, 146, 150, 136, 171, 172, 173, 174,and 180 as well as their respective propellers 152, 142, 144, 148, 134,175, 176, 177, 178, and 179. In an embodiment, propellers 152, 134, 178,and 179 may be variable pitch propellers and propellers 142, 144, 148,175, 176, and 177 may be fixed pitch propellers. In an embodiment,propellers 142, 144, 148, 175, 176, and 177 may fold down when not inuse, such as during wing born flight. Propellers 152, 134, 142, 144,148, 178, 179, 175, 176, and 177 may have any number of blades, such astwo blades, three blades, etc. In an embodiment, the aircraft 100 mayinclude flaperons 118, 119, 120, 121, 122, and 123 on the wing andflaperons 126 and 127 on the tail. The flaperons 118, 119, 120, 121,122, and 123 may be disposed on the trailing edge of the wing betweensuccessive nacelles. The flaperons 126 and 127 may be disposed on thetrailing edge of the tail inboard of the tail mounted nacelles. Theaircraft 100 may also include a vertical control surface on the verticaltail section 102 c, such as a rudder 125. The aircraft 100 may include acamera 154 extending from the fuselage 160. In an embodiment, theaircraft 100 may include landing gear, such as retractable nose skids156 and 158.

FIG. 2 is a component block diagram illustrating a front/right lowerperspective view of the embodiment VTOL and cruise efficient aircraft100 shown with a cutaway view of the fuselage 160. In FIG. 2 theaircraft 100 may be configured for the wing born flight phase withpropellers 142, 144, 148, 176, 177, 134, and 179 folded back againsttheir respective pylons. In an embodiment, two primary power sources 210and 212 may be comprised of internal combustion engines, such as twoeight horse power diesel engines, coupled to two generators. Thefuselage 160 may include a fuel tank 206 storing fuel for the primarypower sources 210 and 212. The primary power sources 210 and 212 may beconnected via wires and various controllers (not shown) to each of theelectric motors and may provide power to drive the propellers. In anembodiment, batteries may be housed in each nacelle, such as batteries214, 216, 218, 220, and 222 and their mirrored counterparts on theopposite side wing section 101 b and horizontal tail section 102 b.These batteries may also be connected to the electric motors via wiresand various controllers (not shown) and may provide power to drive thepropellers. Together the primary power sources 210 and 212 and variousbatteries may comprise a battery augmented series hybrid electricpropulsion system for the aircraft 100. The aircraft 100 may include asatellite communication system comprised of various modules 204 and 208,and the aircraft may carry a payload 202. As illustrated in FIG. 2, theskids 156 and 158 may retract up to the fuselage 160 during wing bornflight.

In an embodiment, the airfoil may be a custom designed shape to be atradeoff between low drag at high lift coefficients, ease of wingfabrication, and gradual stall characteristics. In an embodiment, motorpylons may be shaped to minimize drag at high lift coefficients.Normally, when mounting pylons or nacelles at the leading edges of thewings, the pylons or nacelles mature the boundary layer and cause theairflow over the wing to separate early leading to a loss of lift and anincrease in drag. In an embodiment, the area of the cross section of thepylons may vary from forward to aft. As an example shown in FIG. 3, thepylons of the various embodiments may have a bottle-type configuration(or shape) where the cross sectional area may be comparatively less inthe middle portion A of the pylon than in a forward or aft section ofthe pylon which may minimize the super velocity around the pylon, thusreducing the drag between the wing and the pylon. The bottleconfiguration (or shape) of the pylons may reduce the drag due tointeraction with the wing. The airflow must accelerate to move aroundthe thick regions, and it may be desirable to not have the thick regionof the wing in the same place as the thick region of the pylons. Thebottle configuration (or shape) may enable the thick regions of thepylon to be moved away from the thick region of the wing. When the winghas its proverse pressure gradient, the pylons may be shaped to have anadverse pressure gradient and when the wing has its adverse pressuregradient, the pylons may be shaped to have a proverse pressure gradient.

FIG. 4 is a component block diagram illustrating a front view of theembodiment VTOL and cruise efficient aircraft 100 in the wing bornflight phase. In an embodiment, during wing born flight, the propellers142, 144, 146, 134, 177, 176, 175, and 179 may fold down and only thepropellers 152 and 178 may operate.

FIG. 5 is a component block diagram illustrating a left side view of theembodiment VTOL and cruise efficient aircraft 100 in a VTOL flightphase. In the VTOL flight phase the wing and horizontal tail sectionsmay be tilted up, such as to 90 degrees. In an embodiment, thepropellers 175, 176, 177, 178, and 179 (and their right sidecounterparts), may all be driven by their respective motors in the VTOLflight phase. In another embodiment, the propellers 175, 176, 177, and179 (and their right side counterparts) may be driven by theirrespective motors in the VTOL flight phase, while propeller 178 (and itsright side counterpart) may not be driven by their respective motors. Inan embodiment, the skids 156 and 158 and vertical tail surface 102 c maybe configured to support the aircraft 100 on the ground and the outboardwing nacelles may be configured to act as outboard landing skids. DuringVTOL flight, pitch may be controlled by the fore and/or aft propellerthrust modulation, roll may be controlled by left and/or right propellerthrust modulation, and yaw may be controlled by counter clock wise andclock wise rotation of the various propellers and the flaperons. In anembodiment, yaw may also be controlled by differential deflection of theflaperons.

FIG. 6 is a component block diagram illustrating a left side view of theembodiment VTOL and cruise efficient aircraft 100 transitioning betweenthe VTOL flight phase and a wing born flight phase. During thetransition between VTOL flight and wing born flight the wing andhorizontal tail surfaces may tilt (for example tilt down to transitionfrom VTOL flight to wing born flight and tilt up to transition from wingborn flight to VTOL flight). In an embodiment, the propellers 175, 176,177, 178, and 179 (and their right side counterparts), may all be drivenby their respective motors in the transition phase. In anotherembodiment, less than all the propellers may be driven during thetransition. Additionally, the landing skids 156 and 158 may retract.

FIG. 7 is a component block diagram illustrating a left side view of theembodiment VTOL and cruise efficient aircraft 100 in the wing bornflight phase. The wing and horizontal tail sections may be tilted downand the propellers 175, 176, 177, and 179 (and their right sidecounterparts) may be stopped and folded back wing born flight phase,while propeller 178 (and its right side counterpart) may be driven bytheir respective motors to provide the necessary propulsion for wingborn flight. During wing born flight, pitch may be controlled byelevators for quick changes and/or by tail rotation for slow rotation,roll may be controlled by the flaperons, and yaw may be controlled bythe rudder.

In an embodiment, the aircraft 100 may be an unmanned aerial vehicle,sized to for ease of vehicular roadway transportation. For example, theaircraft 100 may have a tow weight of less than or equal to two hundredand fifty pounds and may break down into no more than three storageboxes. Aircraft 100 may have a set up and launch time of less than sixtyminutes by two trained operators, including off load, assembly, fueling,system checks, and start up. The operators may locally direct takeoff ofthe aircraft 100 then transfer control to a remote location viasatellite data link. During recovery the operators may receive controllocally to direct the landing, and landing and vehicle breakdown maytake less than thirty minutes for two trained operators, including shutdown, drainage of fuel, disassemble, and loading of the aircraft 100.

In an embodiment, a payload of the aircraft 100 may be a science payloadof twenty-five pounds, requiring five hundred watts of power, and havinga volume of 2500 cubic inches. The aircraft 100 may also carry acommunications payload of thirty five pounds and requiring two hundredand seventy watts of power. In an embodiment, the aircraft 100 may havea small launch/recovery footprint defined by a twenty foot by twentyfoot box. The aircraft 100 may provide landing accuracy and sensorplacement within 1.5 meters of an intended location. The aircraft 100may provide for loiter missions and/or sensor placement missions. In anembodiment, the aircraft 100 may be able to fly only on the secondarypower source of the electricity from the batteries during wing bornflight for short periods of time in order to fly quietly. In anembodiment, the aircraft may be able to climb to 100 feet beforetransitioning to wing born flight.

FIGS. 8-14 illustrate various views of an embodiment tri-rotor vehicle,such as tri-rotor aircraft 800. FIG. 8 is a component block diagramillustrating a top view of an embodiment tri-rotor aircraft 800including a front rotor 802 and two tail rotors 812. The tri-rotoraircraft 800 may include a fixed wing 806, fuselage 807, and tail 810.The fixed wing 806 may include ailerons for controlling roll. The frontrotor 802 may be mounted at the front of the fuselage 807 on a hingedportion of the fuselage 807 that may house the motor 804 driving thefront rotor 802. The motor 804 may be a fuel burning motor, such as aCosworth engine, or an electric engine. The two tail rotors 812 may bemounted on the tail 810. In addition to the engine 804, the fuselage 807of the tri-rotor aircraft 800 may house may include a payload 805,satellite communication system 808, fuel tank 813 for the engine 804,and camera turret 814 (shown in FIG. 9A).

FIG. 9A is a component block diagram illustrating a front/left upperperspective view of the tri-rotor aircraft 800 in the wing born flightconfiguration phase, and FIG. 9B is a front/left upper perspective viewof the tri-rotor aircraft 800 in a VTOL flight configuration or phase.As illustrated in FIG. 9A, during the wing born flight phase the frontrotor 802 may be tilted down, and as illustrated in FIG. 9B, during theVTOL flight phase the front rotor 802 may be tilted up. FIG. 10 is acomponent block diagram illustrating a front view of the tri-rotoraircraft 800. As illustrated in FIG. 10, the tail 810 may be a v-tailstructure with a vertical tail extending down from the v-tail surfaces.The vertical section of the tail extending down from the v-tail surfacesmay include a rudder for controlling yaw.

FIG. 11 is a component block diagram illustrating a rear/left upperperspective view of the tri-rotor aircraft 800. The tail rotors 812 maybe mounted on pylons extending from the v-tail surfaces of the tail 810.The pylons may house the motors driving the tail rotors 812, such aselectric motors or fuel burning engines. The tail rotors 812 may beSamara type VTOL rotors which may be left exposed during cruise (i.e.,not stowed). The tail rotors 812 may, or may not, be pitch and/or RPMcontrollable rotors. The motors driving the tails rotors 812 and frontrotor 802 can be a combination of electric motors and fuel burningengines. In various embodiments, the tail rotors 812 may tilt, forexample, forward, aft, starboard, port, and/or combinations ofdirections. Tilting of the tail rotors 812 and/or the front rotor 802,may change the orientation of the total sum force vector for theaircraft 800. For example, the two tail rotors 812 may vector in boththe forward and aft direction and the starboard and port direction whichmay provide yaw control. This may enable a variety of potential flightconfigurations for forward flight (i.e., wing born flight),including: 1) a forward flight configuration in which the front rotor802 is turned off, and not rotated down while the two aft rotors 812 arekept on and rotated to a forward thrust position; 2) a forward flightconfiguration in which the front rotor 802 is rotated down and kept onwhile the two aft rotors 812 are not rotated and shut down; and 3) aforward flight configuration in which all three rotors 802 and 812 arerotated into a forward facing position and kept on for forward flight(i.e., wing born flight).

FIG. 12 is a component block diagram illustrating a left side view ofthe tri-rotor aircraft 800 in a VTOL flight phase. In the VTOL flightphase, front rotor 802 and engine 804 may be tilted up through a rangeof motion. The range of motion may be any range of motion, such as lessthan 90 degrees, 90 degrees, approximately 90 degrees, greater than 90degrees, etc. The range of motion of the front rotor 802 may be lessthan 90 degrees in various embodiments in which the two tail rotors 812may tilt forward and aft to provide a total sum force vector in thevertical direction. In an embodiment, the front rotor 802 and engine 804may be tilted up in a portion of the fuselage 807 on a hinged structurecontrolled by an actuator 815, such as an extension arm, etc., to tiltfrom horizontal to vertical positions such that the front rotor 802 axismay be oriented vertically (e.g., perpendicular) to the fuselage 807. Inan embodiment, the front rotor 802 and tail rotors 812 may all be drivenby their respective motors in the VTOL flight phase. In the VTOL flightphase, the tail rotors 812 may be activated. Roll control and/or pitchcontrol in the VTOL phase may be provided by speed control on the tailrotors 812. Yaw control in the VTOL phase may be provided by speedcontrol on the tail rotors 812, as well as the physical mounting of thetail rotors 812, for example with a 20 degree cant. In an embodiment,the skids or other landing gear and the vertical surface of the tail 810may be configured to support the aircraft 800 on the ground.

FIG. 13 is a component block diagram illustrating a left side view ofthe embodiment tri-rotor aircraft 800 transitioning between the VTOLflight phase and a wing born flight phase. During the transition betweenVTOL flight and wing born flight the hinged portion of the fuselage 807with the front rotor 802 and engine 804 may tilt (for example tilt downto transition from VTOL flight to wing born flight and tilt up totransition from wing born flight to VTOL flight). In an embodiment, thefront rotor 802 and tail rotors 812, may all be driven by theirrespective motors in the transition phase. In another embodiment, lessthan all the rotors may be driven during the transition. Additionally,the landing skids or other type landing gear may retract or extend.

FIG. 14 is a component block diagram illustrating a left side view ofthe embodiment tri-rotor aircraft 800 in the wing born flight phase. Inthe wing born flight phase, the hinged portion of the fuselage 807 withthe front rotor 802 and engine 804 may be tilted down such that thefront rotor 802 axis may be oriented horizontally (e.g., parallel) alongthe fuselage 807 and the front rotor 802 may act as a propeller, whilethe tail rotors 812 may be deactivated. During wing born flight, pitchmay be controlled by elevators on the tail 810, roll may be controlledby the ailerons, and yaw may be controlled by the rudder on the tail810.

FIGS. 15-17 illustrate various views of another embodiment tri-rotorvehicle, such as tri-rotor aircraft 1500. FIG. 15 is a component blockdiagram illustrating a front/left upper perspective view of aircraft1500 in a wing born flight phase. Aircraft 1500 may include a frontrotor 1502 and two tail rotors 1506. The tri-rotor aircraft 1500 mayinclude a fixed wing 1503, fuselage 1504, and tail 1505. Similar toaircraft 800 described above, in aircraft 1500 the front rotor 1502 maybe mounted at the front of the fuselage 1504 on a hinged portion of thefuselage 1504 that may house the motor driving the front rotor 1502. Thetwo tail rotors 1506 may be mounted on the tail 1505. The aircraft 1500may also include landing gear 1507.

In the wing born flight phase, the hinged portion of the fuselage 1504with the front rotor 1502 and engine may be tilted down such that thefront rotor 1502 axis may be oriented horizontally (e.g., parallel)along the fuselage 1504 and the front rotor 1502 may act as a propeller,while the tail rotors 1506 may be deactivated (e.g., allowed toweathervane, oriented such that the long axis is aligned with the airflow (e.g., via the use of the motor magnets, external magnets, or otherfixtures), etc.). FIG. 16 is a component block diagram illustrating afront/left upper perspective view of the tri-rotor aircraft 1500 in aVTOL flight phase. In the VTOL flight phase, front rotor 1502 and enginemay be tilted up, such as to 90 degrees. In an embodiment, the frontrotor 1502 and engine may be tilted up in a portion of the fuselage 1504on a hinged structure controlled by an actuator 1508, such as anextension arm, etc., to tilt from horizontal to vertical positions suchthat the front rotor 1502 axis may be oriented vertically (e.g.,perpendicular) to the fuselage 1504. In an embodiment, the front rotor1502 and tail rotors 1506 may all be driven by their respective motorsin the VTOL flight phase. FIG. 17 is a component block diagramillustrating a left side view of the tri-rotor aircraft 1500 in a VTOLflight phase. In FIG. 17, the engine 1509 mounted in a pylon of the tail1505 to drive the left tail rotor 1506 is illustrated.

FIGS. 18-20 illustrate various views of another embodiment tri-rotorvehicle, such as tri-rotor aircraft 1800. FIG. 18 is a component blockdiagram illustrating a front/left upper perspective view of thetri-rotor aircraft 1800 in a VTOL flight phase, FIG. 19 is a componentblock diagram illustrating a front/left upper perspective view of t thetri-rotor aircraft 1800 in a wing born flight phase, and FIG. 20 is acomponent block diagram illustrating a top view of the tri-rotoraircraft 1800 in a wing born flight phase. Aircraft 1800 may include afront rotor 1802 and two tail rotors 1807. The tri-rotor aircraft 1800may include a fixed wing 1801, fuselage 1806, and tail 1808. In anembodiment, the wing of aircraft 1800 may be a forward swept wing. In anembodiment, the tail rotors 1807 may be Samara type VTOL rotors. Similarto aircrafts 800 and 1500 described above, in aircraft 1800 the frontrotor 1802 may be mounted at the front of the fuselage 1806 on a hingedportion 1803 of the fuselage 1806 that may house the motor driving thefront rotor 1802. The two tail rotors 1807 may be mounted on the tail1808. The aircraft 1800 may also include landing skids 1804 that may beextended in the VTOL phase and retracted in the wing born flight phase.In the VTOL flight phase, front rotor 1802 and engine may be tilted up,such as to 90 degrees. In an embodiment, the front rotor 1802 and enginemay be tilted up in the hinged portion 1803 by an actuator, such as anextension arm, etc., to tilt from horizontal to vertical positions suchthat the front rotor 1802 axis may be oriented vertically (e.g.,perpendicular) to the fuselage 1806. In an embodiment, the front rotor1802 and tail rotors 1807 may all be driven by their respective motorsin the VTOL flight phase.

In an embodiment, the center of gravity (CG) of the aircraft 1800 may be1.53 ft aft of the front motor 1802 rotation point. The CG range may be+/−0.05 ft. The weight of the aircraft 1800 may be 31 lbs. The wingloading may be 4.7 lbs/ft² and the disk loading may be 2.0 lbs/ft². Thestall speed may be approximately 60 ft/sec (35 kts), and the aircraft1800 may cruise at approximately 75 ft/sec (44 kts). The lift to dragratio (L/D) should approximately be 16. The fuselage 1806 may beconstructed to two primary segments. The forward fuselage may be thehinged portion 1803 that rotates with the front rotor 1802, while themain portion of the fuselage 1806 remains stationary. Fuselage 1802length, from tip of spinner to tip of tail cone, may be 5.59 ft. Themain fuselage 1802 may have a cutout for the wing carry through. Thecutout may be shaped to hold the wing at a 6 degree incidence angle. Theconstruct of the wing 1801 may be with a 3 degree twist (i.e. the wingtips are at a 3 degree trailing edge up than the wing root). There mayalso be 0 degrees of dihedral in the wing 1801. There may be −5 deg ofsweep at the 25% chord location (leading edge of tip airfoil may be0.3005 feet forward of leading edge of root airfoil). Thus, thereference area may equal 6.54 ft², the half span may be 4.955 ft, thewing carry over span may be 0.35 ft, the flap span may be 2.3025 ft, theaileron span may be 2.3025 ft, the root chord may be 0.85 ft, the tipchord may be 0.4406 ft, and the wing carry through chord may be 0.55 ft.The wing carry over may use the same root airfoil, but cut away 0.3 ftfrom the trailing edge. Flaps and ailerons may be incorporated into thewing 1801. The flaps and ailerons may be 15% of the local chord length.In order to prevent the need for custom high torque servos, the flap maybe installed separate from the aileron with independent servos. This mayalso give the ability to program differential flaperons (e.g., use 4channels (1 for left aileron, 1 for left flap, 1 for right flap and 1for right aileron). The leading edge of the wing root may be 1.47 ft aftof the front motor rotation point.

The tail 1808 may be constructed with 0 twist, 0 dihedral, andun-tapered. The chord length of both the horizontal and verticalportions of the tail 1808 may be 0.55 ft. The span of the horizontaltail may be 2.1 ft. Note this span does not include the pods that fairover the rear lift motors. The span of the vertical tail may be 1.85 ft.The elevators and rudders may be 50% of the chord length. The Elevatormay need to move through +10 to −90 degrees. Note+ is trailing edge up.For hover the elevator may need to be −90 degs. For forward flight theelevator may need to move to +/−10 degs. The rudder may move +/−10 degs.The same templates may be used for the horizontal and vertical tails. Inorder to make the vehicle easier to fly, elevator and rudder extensionsmay be used. These extensions may be analogous to training wheels on abike. These extensions may increase the elevator and rudder chord by0.25 ft. These extensions may be attached to the elevators and ruddersin a removable way or may be new elevators and rudders that may beswapped out with the proper size elevators and rudders. For hoverflights, the bottom of the vertical tail may be one of the three landingpoints along with the two front skids 1804. The bottom of the verticaltail may be reinforced in order to protect the rudder when it is restingon the ground. These skids 1804 may retract inward and aft into slots inthe fuselage 1806. The aircraft 1800 may be at rest on the skids 1804with waterline 0 of the fuselage 1806 parallel to the ground. Theleading edge of the horizontal tail may be 4.22 ft aft of the frontmotor rotation point. The leading edge of the vertical tail may be 4.02ft aft of the front motor rotation point. This aircraft 1800'sconfiguration may be prone to have a center of gravity too far aft.Removing excess weight from the tail may adjust the center of gravity.

The preceding description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the following claims and theprinciples and novel features disclosed herein.

What is claimed is:
 1. A tri-rotor vehicle, comprising: a wing having norotors coupled thereto; a tail comprising two horizontal tail sections;a fuselage; two tail rotors coupled to the tail; wherein the twohorizontal tail sections extend horizontally relative to the fuselageand from opposite sides of the fuselage, wherein each of the two tailrotors has a single corresponding respective horizontal tail section,and wherein each of the two tail rotors is coupled only to its ownrespective one of the two horizontal tail sections; and a front rotorcoupled to the fuselage, wherein the front rotor is configured to tiltthrough a range of motion.
 2. The tri-rotor vehicle of claim 1, whereinthe vehicle is configured to transition between a wing born flight phaseand a VTOL flight phase by the front rotor tilting through the range ofmotion.
 3. The tri-rotor vehicle of claim 2, wherein the front rotor iscoupled to a front hinged portion of the fuselage controlled by anactuator to tilt through the range of motion.
 4. The tri-rotor vehicleof claim 3, wherein at least one tail rotor is configured to tiltthrough a range of motion.
 5. The tri-rotor vehicle of claim 4, whereinthe two tail rotors are coupled to the tail such that rotor axes of eachof the two tail rotors are configured to orient vertically relative tothe fuselage during the VTOL flight phase and horizontally during thewing born flight phase.
 6. The tri-rotor vehicle of claim 1, wherein thetwo tail rotors are Samara VTOL rotors.
 7. The tri-rotor vehicle ofclaim 1, wherein the two tail rotors are configured to weathervaneduring a wing born flight phase.
 8. The tri-rotor vehicle of claim 1,wherein the two tail rotors are configured to be stowed in pods on thetail during a wing born flight phase.
 9. The tri-rotor vehicle of claim8, wherein the two tail rotors are held in place by one or more magnetssuch that a long axis of each of the two tail rotors is aligned withairflow over the vehicle.
 10. The tri-rotor vehicle of claim 5, whereinthe front rotor and two tail rotors are not pitch controlled rotors. 11.The tri-rotor vehicle of claim 10, wherein the two tail rotors arecoupled to the tail at a canted angle.
 12. The tri-rotor vehicle ofclaim 1, wherein the front rotor and two tail rotors are cyclic andcollective controlled rotors.
 13. The tri-rotor vehicle of claim 5,wherein the tail is a v-tail.
 14. The tri-rotor vehicle of claim 5,wherein the wing is swept.
 15. The tri-rotor vehicle of claim 5, whereinthe vehicle is an unmanned aerial vehicle.
 16. The tri-rotor vehicle ofclaim 5, further comprising retractable landing skids, wherein the tailis configured to act as a rear landing skid.
 17. The tri-rotor vehicleof claim 12, further comprising a front rotor motor configured todirectly drive the front rotor and two tail rotor motors, each tailrotor motor configured to drive a respective one of the tail rotors,wherein the front rotor motor is a fuel burning engine and each of thetwo tail rotor motors is selected from the group consisting of a fuelburning engine and an electric motor.
 18. The tri-rotor vehicle of claim4, wherein: the two tail rotors are coupled to the tail such that thetwo tail rotors are configured to tilt forward, aft, starboard, andport; and during the wing born flight phase, the front rotor and the twotail rotors are configured to operate in one of: the front rotor istilted up and is deactivated while the two tail rotors are activated andtilted forward; the front rotor is tilted down and activated while thetwo tail rotors are tilted such that rotor axes of each of the two tailrotors are oriented vertically relative to the fuselage and the two tailrotors are deactivated; and the front rotor is tilted down, the two tailrotors are tilted forward and the front rotor and the two tail rotorsare activated.
 19. A tri-rotor vehicle, comprising: a wing having norotors coupled thereto; a tail comprising two horizontal tail sections;a fuselage; two tail rotors coupled to the tail, wherein the twohorizontal tail sections extend horizontally relative to the fuselageand from opposite sides of the fuselage, wherein each of the two tailrotors has a single corresponding respective horizontal tail section,and wherein each of the two tail rotors is coupled only to its ownrespective one of the two horizontal tail sections; and a front rotorcoupled to a front hinged portion of the fuselage controlled by anactuator, wherein the front rotor is configured to tilt through a rangeof motion by control of the actuator and wherein the vehicle isconfigured to transition between a wing born flight phase and a VTOLflight phase by the front rotor tilting through the range of motion; anda front rotor motor configured to drive the front rotor and two tailrotor motors, each tail rotor motor configured to drive a respective oneof the tail rotors, wherein the front rotor motor is selected from thegroup consisting of a fuel burning engine and an electric motor and eachof the two tail rotor motors is selected from the group consisting of afuel burning engine and an electric motor, wherein: the two tail rotorsare coupled to the tail such that rotor axes of each of the two tailrotors are configured to orient vertically relative to the fuselageduring the VTOL flight phase and horizontally during the wing bornflight phase; and the front rotor and two tail rotors are cyclic andcollective controlled rotors.